New ViewModel for loading feed preferences across lifecycle

app/build.gradle

@@ -139,6 +139,11 @@ dependencies {
     implementation "com.android.support:gridlayout-v7:$supportVersion"
     implementation "com.android.support:recyclerview-v7:$supportVersion"
     compileOnly 'com.google.android.wearable:wearable:2.2.0'
+
+    // ViewModel and LiveData
+    implementation "android.arch.lifecycle:extensions:$lifecycle_version"
+    annotationProcessor "android.arch.lifecycle:compiler:$lifecycle_version"
+
     implementation "org.apache.commons:commons-lang3:$commonslangVersion"
     implementation("org.shredzone.flattr4j:flattr4j-core:$flattr4jVersion") {
         exclude group: "org.json", module: "json"

app/src/main/java/de/danoeh/antennapod/activity/FeedSettingsActivity.java

@@ -1,5 +1,6 @@
 package de.danoeh.antennapod.activity;
 
+import android.arch.lifecycle.ViewModelProviders;
 import android.graphics.LightingColorFilter;
 import android.os.Bundle;
 import android.support.v4.app.FragmentManager;
@@ -7,7 +8,6 @@ import android.support.v4.app.FragmentTransaction;
 import android.support.v7.app.AppCompatActivity;
 import android.text.TextUtils;
 import android.util.Log;
-
 import android.view.MenuItem;
 import android.view.View;
 import android.widget.ImageView;
@@ -19,10 +19,8 @@ import de.danoeh.antennapod.core.feed.Feed;
 import de.danoeh.antennapod.core.glide.ApGlideSettings;
 import de.danoeh.antennapod.core.glide.FastBlurTransformation;
 import de.danoeh.antennapod.core.preferences.UserPreferences;
-import de.danoeh.antennapod.core.storage.DBReader;
 import de.danoeh.antennapod.fragment.FeedSettingsFragment;
-import io.reactivex.Maybe;
+import de.danoeh.antennapod.viewmodel.FeedSettingsViewModel;
-import io.reactivex.MaybeOnSubscribe;
 import io.reactivex.android.schedulers.AndroidSchedulers;
 import io.reactivex.disposables.Disposable;
 import io.reactivex.schedulers.Schedulers;
@@ -46,7 +44,6 @@ public class FeedSettingsActivity extends AppCompatActivity {
         super.onCreate(savedInstanceState);
         setContentView(R.layout.feedsettings);
         getSupportActionBar().setDisplayHomeAsUpEnabled(true);
-        long feedId = getIntent().getLongExtra(EXTRA_FEED_ID, -1);
 
         imgvCover = findViewById(R.id.imgvCover);
         txtvTitle = findViewById(R.id.txtvTitle);
@@ -57,14 +54,8 @@ public class FeedSettingsActivity extends AppCompatActivity {
         // https://github.com/bumptech/glide/issues/529
         imgvBackground.setColorFilter(new LightingColorFilter(0xff828282, 0x000000));
 
-        disposable = Maybe.create((MaybeOnSubscribe<Feed>) emitter -> {
+        long feedId = getIntent().getLongExtra(EXTRA_FEED_ID, -1);
-                    Feed feed = DBReader.getFeed(feedId);
+        disposable = ViewModelProviders.of(this).get(FeedSettingsViewModel.class).getFeed(feedId)
-                    if (feed != null) {
-                        emitter.onSuccess(feed);
-                    } else {
-                        emitter.onComplete();
-                    }
-                })
                 .subscribeOn(Schedulers.io())
                 .observeOn(AndroidSchedulers.mainThread())
                 .subscribe(result -> {
@@ -91,10 +82,6 @@ public class FeedSettingsActivity extends AppCompatActivity {
         fragmentTransaction.commit();
     }
 
-    public Feed getFeed() {
-        return feed;
-    }
-
     private void showHeader() {
         txtvTitle.setText(feed.getTitle());
 

app/src/main/java/de/danoeh/antennapod/fragment/FeedSettingsFragment.java

@@ -1,5 +1,6 @@
 package de.danoeh.antennapod.fragment;
 
+import android.arch.lifecycle.ViewModelProviders;
 import android.content.Context;
 import android.content.DialogInterface;
 import android.os.Bundle;
@@ -7,7 +8,6 @@ import android.support.v14.preference.SwitchPreference;
 import android.support.v7.preference.ListPreference;
 import android.support.v7.preference.PreferenceFragmentCompat;
 import de.danoeh.antennapod.R;
-import de.danoeh.antennapod.activity.FeedSettingsActivity;
 import de.danoeh.antennapod.core.dialog.ConfirmationDialog;
 import de.danoeh.antennapod.core.feed.Feed;
 import de.danoeh.antennapod.core.feed.FeedFilter;
@@ -16,6 +16,9 @@ import de.danoeh.antennapod.core.preferences.UserPreferences;
 import de.danoeh.antennapod.core.storage.DBWriter;
 import de.danoeh.antennapod.dialog.AuthenticationDialog;
 import de.danoeh.antennapod.dialog.EpisodeFilterDialog;
+import de.danoeh.antennapod.viewmodel.FeedSettingsViewModel;
+
+import static de.danoeh.antennapod.activity.FeedSettingsActivity.EXTRA_FEED_ID;
 
 public class FeedSettingsFragment extends PreferenceFragmentCompat {
     private static final CharSequence PREF_EPISODE_FILTER = "episodeFilter";
@@ -26,17 +29,21 @@ public class FeedSettingsFragment extends PreferenceFragmentCompat {
     public void onCreatePreferences(Bundle savedInstanceState, String rootKey) {
         addPreferencesFromResource(R.xml.feed_settings);
 
-        feed = ((FeedSettingsActivity) getActivity()).getFeed();
+        long feedId = getArguments().getLong(EXTRA_FEED_ID);
-        feedPreferences = feed.getPreferences();
+        ViewModelProviders.of(getActivity()).get(FeedSettingsViewModel.class).getFeed(feedId)
+                .subscribe(result -> {
+                    feed = result;
+                    feedPreferences = feed.getPreferences();
 
-        setupAutoDownloadPreference();
+                    setupAutoDownloadPreference();
-        setupKeepUpdatedPreference();
+                    setupKeepUpdatedPreference();
-        setupAutoDeletePreference();
+                    setupAutoDeletePreference();
-        setupAuthentificationPreference();
+                    setupAuthentificationPreference();
-        setupEpisodeFilterPreference();
+                    setupEpisodeFilterPreference();
 
-        updateAutoDeleteSummary();
+                    updateAutoDeleteSummary();
-        updateAutoDownloadEnabled();
+                    updateAutoDownloadEnabled();
+                }).dispose();
     }
 
     private void setupEpisodeFilterPreference() {

app/src/main/java/de/danoeh/antennapod/viewmodel/FeedSettingsViewModel.java

@@ -0,0 +1,30 @@
+package de.danoeh.antennapod.viewmodel;
+
+import android.arch.lifecycle.ViewModel;
+import de.danoeh.antennapod.core.feed.Feed;
+import de.danoeh.antennapod.core.storage.DBReader;
+import io.reactivex.Maybe;
+
+public class FeedSettingsViewModel extends ViewModel {
+    private Feed feed;
+
+    public Maybe<Feed> getFeed(long feedId) {
+        if (feed == null) {
+            return loadFeed(feedId);
+        } else {
+            return Maybe.just(feed);
+        }
+    }
+
+    private Maybe<Feed> loadFeed(long feedId) {
+        return Maybe.create(emitter -> {
+            Feed feed = DBReader.getFeed(feedId);
+            if (feed != null) {
+                this.feed = feed;
+                emitter.onSuccess(feed);
+            } else {
+                emitter.onComplete();
+            }
+        });
+    }
+}

build.gradle

@@ -45,6 +45,7 @@ project.ext {
     targetSdkVersion = 26
 
     supportVersion = "27.1.1"
+    lifecycle_version = "1.1.1"
     workManagerVersion = "1.0.1"
     awaitilityVersion = "3.1.2"
     commonsioVersion = "2.5"